1. Field of the Invention
The present invention relates to a method for determining the representative color of a metallic paint whose color varies with the angle of observation, a method for classifying and arranging metallic paint colors, and a computer graphic apparatus.
The invention further relates to a computer graphic apparatus for calculating the representative one of metallic paint colors as a hue-tone value, arranging computer graphics of metallic colors expressing their textures on a hue-tone chart, and thereby displaying a chromatological classification of colors and their textures at the same time.
The invention, since it permits identification of the representative color of a paint which contains various effective pigments such as aluminum flakes, mica flakes and plate iron oxide in the coat and whose color varies with the angle of observation, makes possible classification and arrangement of colors and computerized search of colors. Furthermore, the invention provides a computer-based design tool capable of simultaneously evaluating color and texture by superposing computer graphics accompanied with textures.
2. Description of the Prior Art
The colors of the body coating of automobiles in recent years are characterized by the dominance of metallic paints containing various effective pigments (including aluminum flakes, mica flakes and graphite). A metallic paint varies in color with the angle of observation, gives metallic luster, pearly luster or bicolor appearance (an effect to exhibit two or more colors depending on the angle), and this feature is known as texture. As techniques of chromatological classification of the body colors of automobiles, the Munsell scale and the hue-tone scale have been extensively used for many years.
Solid coating colors can be classified according to a system of color chips prepared with solid pigments. However, it is difficult to extract the representative one out of various colors which a metallic paint would manifest with changes in the angle of observation. Reported methods for classification of others than solid colors including ones for classifying angle-dependent colors for the purpose of grading pearls (Japanese Laid-open [KOKAI] Patent Publication No. 061635/81 and Japanese Laid-open [KOKAI] Patent Publication No. 230778/86), but none of these methods is applicable to so diverse colors as those of automobile body coating.
For this reason, the conventional practice is for the designer to look at metallic paint colors one by one against light, observe color variation from highlight to shade by the eye and, after imaging the representative one of the various colors in his or her head, to finally determine the hue-tone value. This method, however, involves the disadvantages of taking too long a time and variance in results with the designer who appraises the color.
Furthermore, when the designer searches for a color he or she images out of a tremendous variety of paint colors prepared in the past, as the search takes so many man-hours per color checked as the above-described procedure requires, the designer has no other alternative than to make a rough guess to pick out the color he or she remembers, and accordingly is substantially deterred from retrieving the true color.
To sum up the problems noted above, the biggest point is how to determine the representative color of a metallic paint whose color varies with the angle of observation. In a colorimetric approach, if an answer can be given to the question of the colorimetric value taken in what angle can give the representative value of that coating color, the value of that color can be figured out in terms of HVC in the Munsell color scale or the commercial available hue-tone scale, and a color whose value coincides with this calculated value can be chosen as being approximately the imaged color.
According to the present invention, in order to solve the above-stated problems, there is provided a method by which the representative color of any metallic paint color can be determined by a multiple regression formula of the lightness and saturation of the metallic paint color at not fewer than two angles of observation.
According to the invention, in order to solve the above-stated problems, there is provided a method for classifying and arranging metallic paint colors, comprising:
determination of the representative one of the colors of each metallic paint color;
calculation of the hue-tone value of said representative color;
generation of coating color computer graphics representing the optical properties of said metallic paint color in a prescribed range of angles of observation; and
preparation of a coating color map by arranging said coating color computer graphics over the hue-tone value of said representative color in a hue-tone chart on the monitor screen of a computer system.
According to the invention, in order to solve the above-stated problems, there is provided a computer graphic apparatus comprising:
a means to determine said representative color of any metallic paint color out of colorimetric values of said metallic paint color at a plurality of angles of observation;
a means to convert said representative color into a hue-tone value;
a means to generate coating color computer graphics of said metallic paint color from the colorimetric values of said metallic paint color at a plurality of angles of observation; and
a means to arrange and display said coating color computer graphics over the hue-tone value in a hue-tone chart generated on a display unit.
The most important technique of the prevent invention is the method to determine by calculation, when any metallic paint color is given, the degree at which the measured value, out of those values measured at many different angles, can give the representative color of that metallic paint color. This core technique is called the xe2x80x9calgorithm to determine the representative color of a metallic paint.xe2x80x9d
As a result of research through repeated experiments by eye observation of metallic paint colors containing various effective pigments as samples, the development of the xe2x80x9calgorithm to determine the representative color of a metallic paintxe2x80x9d has been successfully accomplished.
Thus, in architecting a computer system to retrieve a designer-imaged color of a metallic paint which contains various effective pigments and whose color varies in many ways with the angle of observation, if the following three items are available, the hue-tone value which is the imaged value can be calculated and, by using this value, conversely any hue-tone value can be retrieved from the reflection factors at many different angles measured in the past:
a) a hard disk for storing the colorimetric values of a metallic paint color at many different angles;
b) an xe2x80x9calgorithm to determine the representative color of a metallic paintxe2x80x9d for calculating the angle of the representative metallic color from those multi-angle data; and
c) an algorithm for calculating the representative color into a hue-tone value.
By adding the following two more items, computer graphics can be pasted on the calculated hue-tone value on the hue-tone chart outputted on a computer graphic monitor screen, and totally novel computer graphics permitting simultaneous appraisal of the hue-tone value, which is a chromatological color class, and of texture can be obtained:
d) computer graphics representing the metallic color variation with each change in angle by the multi-angle reflection factor; and
e) computer graphics of the hue-tone chart.